1. Field of the Invention
The present invention pertains generally to ladders, and more particularly to hunting ladders. In one preferred manifestation, the present invention is a 360 degree pivoting leveling ladder system that provides a substantially level ladder regardless of the orientation of the structure the ladder is mounted onto.
2. Description of the Related Art
Ladders provide a series of spaced bars or rungs that can easily be traversed. These rungs act as lightweight steps that facilitate moving up and down surfaces that are too steep to safely or conveniently traverse. Conventional ladders are designed for leaning on upstanding members such as trees, poles, and other generally vertically oriented structures. In many instances, the vertical distance being traversed is greater than would be convenient for a single section rigid ladder, which must be stored when not in use and transported to and from storage.
Recognizing this limitation and providing a solution, a number of US patents illustrate multiple ladder sections that are coupled end-to-end. These patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 3,995,714 by Brookes et al, entitled “Multi-section ladder for scaling poles”; U.S. Pat. No. 4,411,335 by Forrester, entitled “Hunter's tree stand”; U.S. Pat. No. 5,016,732 by Dunn, entitled “Portable combination hunting and observation stand”; U.S. Pat. No. 5,040,635 by Strickland, entitled “Multisection pole ladder”; U.S. Pat. No. 6,668,975 by Skipper, entitled “Modular ladder with removable rungs”; U.S. Pat. No. 7,717,232 by Butcher, entitled “Ladder stand with optional extension member, kit for constructing height-adjustable ladder stand, and method of using same”; U.S. Pat. No. 8,443,938 by Furseth et al, entitled “Hunting ladder stand having collapsible ladder segments”; U.S. Pat. No. 8,651,259 by Blehm, entitled “Ladder bridge apparatus”; U.S. Pat. No. 8,695,762 by Carter et al, entitled “Upright tree stand”; and Des 590,068 by Woller, entitled “Modular tree ladder”.
These ladders work well when climbing up a surface such as a wall or other building component, and may readily be adapted for different vertical distances. Buildings are generally flat and vertical, and also generally have a flat surface at the base of the vertical face that the ladder can stand upon.
Unfortunately, in contrast to a building, most of the trees in the wild do not grow“plumb”. Setting a conventional ladder in a crooked tree results in the ladder being slanted. This presents a serious hazard to a hunter using a ladder.
When the ladder is tilted, the rungs are also. Sloped rungs are more difficult for a person to safely and securely place their foot upon. In addition, when the conventional ladder is slanted, then the base of the ladder will not be standing flat on the ground. This increases the risk of the ladder shifting and pivoting when a person climbs up the ladder. The combination of sloped rungs and a wobbling base make the ladder extremely dangerous, and may lead to a serious fall. As a result, it is impossible to safely set a conventional ladder in many trees.
One prior art approach to overcome this limitation is to provide a ladder fabricated from a plurality of independent modules. Each module is then suspended independently, and a person climbing the ladder will move from one ladder module to the next. By suspending each module independently, the modules rely upon the vertical support for anchoring, rather than the base or ground. This can eliminate the wobble of the prior art conventional ladders. Exemplary US patents, the teachings and content which are incorporated herein by reference, include: U.S. Pat. No. 317,534 by Hoell, entitled “Fire escape”; U.S. Pat. No. 886,605 by Hersche, entitled “Combined window rest and escape ladder”; U.S. Pat. No. 2,232,414 by Swann, entitled “Ladder anchoring means”; U.S. Pat. No. 3,961,686 by Starkey, entitled “Easy-up tree stand”; U.S. Pat. No. 5,439,072 by Jenkins, entitled “Modular ladder system”; U.S. Pat. No. 5,509,499 by Prejean, entitled “Portable hunter's ladder”; U.S. Pat. No. 5,704,448 by Jenkins, entitled “Modular ladder system”; U.S. Pat. No. 5,711,399 by Wayne-Prejean, entitled “Portable hunter's ladder”; U.S. Pat. No. 5,816,362 by Jenkins, entitled “Modular safety ladder system”; U.S. Pat. No. 6,006,864 by Musk, entitled “Tree ladder attachment”; U.S. Pat. No. 6,547,035 by D'Acquisto, entitled “Ladder module”; and U.S. Pat. No. 7,237,649 by Harmston, entitled “Tree ladder”. Unfortunately, for use upon a tree, these ladders also require anchoring to the tree at both the top and bottom of each module, making the installation more time consuming and difficult. If the installation is not secure within each ladder module, than an individual module may slip or rotate. Since the modules are independent of each other, this may render the ladder structure impassible.
A different approach to overcome the tilt of the tree is to run the ladder away from the tree and provide a pivotal ladder termination, such as illustrated in U.S. Pat. No. 8,528,695 by Orpia, entitled “Ladder safety systems”. This approach allows a person to set a single ladder section against an irregular support such as a tree and upon an uneven ground surface, and angle the ladder termination to securely couple to the tree. This resolves the prior art problem with the wobbling base, but in turn limits the ladder to the single section, since there is no way to then add another section to the ladder to increase vertical climb. Two additional related pivotal terminations are illustrated in U.S. Pat. No. 6,073,725 by Kumher et al, entitled “Multi-position ladder and support therefor”; and 2015/0060201 by Hume, entitled “Self leveling step ladder with a universal hinge joint”; the teachings and contents which are also incorporated herein by reference.
U.S. Pat. No. 6,138,792 by Morris, entitled “Portable climbing apparatus”, the teachings and contents which are incorporated herein by reference, discloses a flexible ladder with multiple sections and multiple straps. This patent offers much benefit over the prior art conventional ladders, by following less than perfectly flat and vertical surfaces, but is still limited to relatively straight trees.
Other exemplary prior art patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 143,112 by Ainsworth, entitled “Fire-escapes”; U.S. Pat. No. 191,181 by Row, entitled “Fire-escape”; U.S. Pat. No. 3,116,808 by Riley, entitled “Portable deer stand”; U.S. Pat. No. 3,294,196 by Rabelos, entitled “Emergency escape ladder and amusement device”; U.S. Pat. No. 5,860,490 by Petti et al, entitled “Monopole ladder”; and U.S. Pat. No. 6,340,071 by Diekemper, entitled “Rung-foldable ladder device”.
In addition to the aforementioned patents, Webster's New Universal Unabridged Dictionary, Second Edition copyright 1983, is incorporated herein by reference in entirety for the definitions of words and terms used herein.